1. Field of the Invention
This invention relates to an image reader for irradiating an original with light beams from a light source lamp and reading data about an image formed on the original based on a reflected light beams and particularly to the structure of a light source lamp for being placed as close to an original as possible.
2. Description of the Related Art
An image reader such as a copying machine or scanner is provided for reading out image data of an original on paper or the like to subject the image data to a various kinds of processing. Generally, the image reader is composed of a light source lamp such as a fluorescent lamp for irradiating an original with light beams and a light receiving station including a photoelectric converter device such as CCD (Charge-Coupled Device). The reflected light beams from the original is guided to enter a light receiving station. There are two types of image readers known in the art, a stationary original type and an moving original type.
The stationary original type image reader is disclosed, for example, in Japanese Patent Laid-Open Publication No. 10-257252. The image processor is designed to irradiate an original placed on a platen glass with light beams from a light source lamp being moved along the original. In addition, the optical path length from the original to a light receiving station should be kept at a constant even though the position for irradiating the original with light beams varies. A reflector or the like is also provided for introducing reflected light beams to the light receiving station. In this type, furthermore, the reflector or the like is designed to move along the original together with the light source lamp. In the case of the moving original type image reader is disclosed, for example, in Japanese Patent Laid-Open Publication No. 8-122938. A light source lamp is fixed on a predetermined position while an original can be moved sequentially to change its position for irradiating the original with light beams from the light source lamp to read image data from the original.
In recent years, it has been required that an image reader obtains image data more accurately because of the need for faithful reproduction of image data when it is reproduced on a display connected to a copying machine or a personal computer.
For attaining accuracy of obtained image data, a person skilled in the art generally increases the amount of light beams from the light source lamp to enhance the brightness of the original. However, the intensity of light from the light source lamp has its own limits. Therefore, it is difficult to obtain image data more accurate than the accurate image date presently obtainable in the art.
An object of the present invention is to provide a light source lamp structure for an image reader that allows the increase in brightness of the exposure to an original by placing the light source lamp as close to an original as possible.
As the technical means for attaining the above object, a first aspect of the present invention is to provide a light source lamp structure of an image reader to read an image formed on a original by irradiating the original placed on a platen glass with light beams from a light source lamp, capturing reflected light beams from the original, followed by introducing the reflected light beams to a light receiving station, and to read an image formed on the original, wherein a cut portion with a predetermined shape is formed on a part of a lamp socket of the light source lamp.
According to the present invention, the lamp socket may be arranged such that the cut portion is positioned in front of the platen glass. In contrast to the conventional lamp socket without such a cut portion, the lamp socket of the present invention can be placed closer to a top plate of a casing in which a platen glass is arranged in place, a distance equivalent only to the length of the cut portion. Such a configuration of the lamp socket permits positioning of the light source lamp closer to the original placed on the platen glass. Consequently, the original can be irradiated with more intense light beams compared with the conventional structure, thereby allowing an increase in brightness of the original.
Furthermore, a second aspect of the present invention is to provide a light source lamp structure of an image reader to read an image formed on a original by irradiating the original placed on a platen glass with light beams from a light source lamp, capturing reflected light beams from the original, followed by introducing the reflected light beams to a light receiving station, and to read an image formed on the original, wherein a cut portion with an appropriate shape is formed on a part of a lamp socket of the light source lamp and a part of a lamp tube of the light source lamp is exposed from the cut portion.
According to the present invention, the light beams to be incident onto the original can be also irradiated from the portion of the lamp tube exposed from the lamp socket. Thus, the irradiation of light beams from the whole area of the lamp tube can be attained, allowing the increase in an effective range of light beams irradiation on the original. Consequently, the original can be irradiated with the large amount of light beams compared with the conventional one, allowing the increase in brightness of the original.
In the light source lamp structure of the image reader according to the present invention, the shape of the cut portion of the lamp socket may be a plane perpendicular to the output optical axis of the light source lamp.
For effectively irradiating the original with light beams, the light source lamp has the directivity of light beams irradiation to prevent structural components such as a carriage on which the light source lamp is mounted from being heated. Such directivity is determined so as to make reflected light beams from the original surely be incident on a reflector and is appropriately inclined from the vertical direction. Furthermore, the positional relationship between the lamp tube and the lamp socket is defined such that the directivity of the light source lamp can be coincident with a predetermined direction by engaging the lamp socket holding the lamp tube with a predetermined bracket at the time of mounting the light source lamp. Therefore, the cut portion can be formed on the plane perpendicular to the output optical axis of the light source lamp by cutting a part of the lamp socket with reference to the portion to be engaged with the bracket of the lamp socket.
In the case of exposing a part of the lamp tube to the plane perpendicular to the output optical axis of the light source lamp, light beams from such an exposed portion is incident on the original to be reflected toward the reflector. Therefore, the brightness of the original can be further increased.
In the light source lamp structure of the image reader according to the present invention, furthermore, the shape of the cut portion may be a plane substantially parallel to a surface of the platen glass opposite to the original placing side thereof, while the light source lamp is arranged in place. Therefore, the plane on which the cut portion is formed is brought into parallel to and is placed closer to the top plate of the casing that includes the platen glass. The result is that the light source lamp can be placed closer to the original on the platen glass, providing an increase in brightness of the original.
In the light source lamp structure of the image reader according to the present invention, the shape of the cut portion may be composed of: a plane perpendicular to the output optical axis of the light source lamp; and a plane substantially parallel to a surface of the platen glass opposite to the original placing side thereof while the light source lamp is being arranged in place.
Therefore, the original can be effectively irradiated with light beams generated from the light source lamp. In addition, the light source lamp can be placed close to an original as much as possible. Therefore, the brightness of the original can be increased at a maximum with the largest amount of illuminating light beams.
These and other features, objects and advantages of the present invention will become apparent upon reading the following description thereof together with reference to the accompanying drawings.